1. Field of the Invention
The invention relates to a method and apparatus for extracting mechanical energy from a pressured gas by expanding same in a plurality of peripherally spaced cylinders mounted for oscillating movement about the axis of an output shaft which is connected to the cylinders.
2. Description of the Prior Art
In pending patent application Ser. No. 560,305, filed Dec. 12, 1983, now U.S. Pat. No. 4,513,576, and assigned to the Assignee of this application, there is disclosed a plurality of configurations of fluid pressure engines wherein a power output is derived by the oscillating movements of one or more cylinders which are mounted for oscillating movement about an axis defined by an output shaft on which the cylinders are mounted. In all such arrangements, a free piston is employed in each of the cylinders. The opening of inlet valves to add a compressed gas to one end of the cylinder and, in some instances, the concurrent control of exhaust valves at the same and opposite ends of the cylinder was effected by solenoid-actuated valves. Such valves were controlled by electronic sensing devices responsive to the piston positions. Moreover, because none of the pistons were in any manner interconnected, special electronic timing mechanisms had to be incorporated in the valve control circuits to insure that the pistons were substantially concurrently energized during each of their power strokes, so as to maintain dynamic balance of the oscillating frame carrying the cylinders.
Computer modeling of several of the configurations disclosed in the aforementioned co-pending application revealed the fact that under certain assumed conditions, the reciprocating movement of the free pistons occurred at such a high rate as to require extremely fast action of the inlet and exhaust valves.
Lastly, and most importantly, since the oscillatable cylinders were connected to a load, the application of fluid pressure force between the cylinders and the pistons resulted in the pistons having a substantially greater stroke than the cylinders, primarily due to the fact that the total piston mass was significantly less than the total effective mass connected to the cylinders. If, for example, the weight of the free pistons were only one-tenth the effective weight of the load and interconnected cylinders which respectively cooperate with the free pistons, the stroke of the cylinders over any given time period would obviously be only one-tenth the stroke of the pistons in the same time period. Thus, while the interconnected cylinders did produce an oscillating torque about the axis of the output shaft, the stroke of the interconnected cylinders, hence the angular stroke of the oscillation of the output shaft, was quite limited in extent and thus limited the number of potential applications of the fluid pressure operated oscillating engine.